By Pat Anson, PNN Editor

Low-dose naltrexone (LDN) continues to get more recognition from the medical community as a treatment for some types of chronic pain.

In a review of 47 studies on the off-label use of LDN, researchers at the University of Kansas Medical Center found “promising results” that naltrexone improves pain and function and reduces symptom severity in patients with chronic inflammatory or centralized pain. Most of the studies were small, however, and larger clinical trials are needed to demonstrate LDN’s efficacy.

“Though the results look promising, further, more well controlled studies are required before formal recommendations can be made,” said lead author Adam Rupp, DO, who will present his findings this week at the annual meeting of the American Society of Regional Anesthesia and Pain Medicine (ASRA) in Orlando, Florida.

Naltrexone is an inexpensive generic drug that is only approved by the Food and Drug Administration as a treatment for substance abuse. In 50mg doses, naltrexone blocks opioid receptors in the brain and decreases the desire to take opiates or alcohol.  

But in smaller doses of 5mg or less, patients with fibromyalgia, interstitial cystitis, intractable pain and other chronic conditions have found LDN to be an effective pain reliever. But because LDN is prescribed “off label” for pain, much of the evidence supporting LDN is anecdotal.

How naltrexone works is not entirely clear, but LDN supporters believe the drug helps modulate the immune system, reducing inflammation and stimulating the production of endorphins, the body's natural painkiller. LDN is not recommended for people currently taking opioid medication because it blocks opioid receptors and may cause withdrawal.

In their literature review, Rupp and his colleagues found that LDN improved physical function, sleep, mood, fatigue and quality of life in patients with Complex Regional Pain Syndrome (CRPS), fibromyalgia, diabetic neuropathy, Crohn’s disease, rheumatoid arthritis and low back pain. In patients with Crohn’s, improvements were also noted in the colon’s appearance during colonoscopies.

Side effects from LDN were minimal, consisting most commonly of vivid dreams, headaches, diarrhea and nausea. Most of the side effects resolved with continued use of LDN.

“The evidence in this review provides support for the off-label use of LDN for various chronic
inflammatory or centralized pain conditions. However, it is apparent that high-quality controlled studies focusing on administration, dosing and follow up time are needed before formal recommendations can be made,” Rupp said.

“Despite the current paucity of high-quality evidence in the literature, LDN continues to offer promising results in the management of symptoms in patients with chronic inflammatory or centralized pain conditions.”

Because LDN is not recommended as a pain treatment by the FDA or professional medical societies, patients interested in trying it often encounter doctors who refuse to prescribe it or don’t know anything about it. The LDN Research Trust includes a list of LDN-friendly doctors and pharmacies on its website.